Basic Electrical Installation Work
332
The cables are very small because the optical quality the conductor is
very high and signals can transmitted over great distances.47. Avoid tight-radius bends possible and kinks
at all costs.
Fire alarm circuits (BS 5839 and 54-2: 1998)
Through one more the various statutory Acts, all public buildings are
required provide effective means giving warning fire that
life and property may protected.
In normally open circuit, the alarm call points are connected parallel
with each other that when any alarm point initiated the circuit com-
pleted and the sounder gives warning fire. 14.
Fire alarm circuits are wired either normally open normally closed. light loss) down the cable. Cables are terminated special joint boxes which ensure
cable ends are cleanly cut and butted together ensure the continuity of
the light pulses. The arrangement shown
in Fig. Single-sheathed cables
are often called ‘simplex’ cables and twin sheathed cables ‘duplex’, that is,
two simplex cables together one sheath.
The testing fibre-optic cables requires that special instruments used
to measure the light attenuation (i. In
a normally open circuit, the alarm call
points are connected parallel with
each other that when any alarm
point initiated the circuit com-
pleted and the sounder gives warn-
ing fire. They are
cheap produce and lightweight because these new cables are made from
high-quality plastic and not high-quality copper.
Fibre-optic cables look like steel wire armour cables (but course are
lighter) and should installed the same way and given the same level
of protection SWA cables. effective system one which gives
a warning fire while sufficient time remains for the fire put out and
any occupants leave the building. Multi-core cables are available
containing single fibres. Fibre-optic cables are Band circuits when used for data
transmission and must therefore segregated from other mains cables to
satisfy the IEE Regulations.47
A simple normally open fire alarm circuit.
.
Definition
Fire alarm circuits are wired either
normally open normally closed.e. essential for some parts the wiring system continue
Alarm
sounders –
bells sirens
Alarm
call
points
Master
control
unit
Secure
supply
FIGURE 14. Finally,
when working with fibre-optic cables, electricians should avoid direct eye
contact with the low-energy laser light transmitted down the conductors
